Factor structure of the Disability and Impact Profile in patients with multiple sclerosis

The Disability and Impact Profile (DIP) is used for the measurement of qual ity of life in multiple sclerosis (MS) patients. Data from 211 persons with definite MS from Belgium, Denmark and the Netherlands were used to address three questions. To what extent do the impairment ratings and their comple mentary weighted scores share common variance? What is the factor structure of the weighted scores? To what extent do disease-related information and information from psychological questionnaires offer concurrent validity for the factors? Correlations between impairment ratings and the weighted item scores were high; for most items the complementary ratings of impact do no t supplement information provided by impairment ratings. The DIP weighted s cores can be represented to some extent by three independent dimensions: a motor (skeletal movement) or displacement ability factor, a factor relating to sensory-cognitive intactness and a psychological well-being factor. A t wo-factor solution provides a first factor identical to that of the three-f actor solution and a second factor representing psychological well-being. T he two factors correlate well with instruments measuring disability and wit h satisfaction versus emotional distress. Provisional scales based on the f actors were constructed. Qual. Life Res. 8:141-150 (C) 1999 Kluwer Academic Publishers.